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  • 11
    Electronic Resource
    Electronic Resource
    Springer
    Marine biology 81 (1984), S. 217-222 
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In the brown alga Dictyota dichotoma Lamour the phaeoplasts move to the anticlinal walls (profile position) in strong light and to the periclinal walls (face position) in dim light. By these movements transmittance changes are caused. If the algae were grown in light:dark cycles of about natural daylengths, circadian oscillations of the amplitudes and the kinetics of these transmittance changes are initiated. The lengths of the free running periods vary between 24 and 29 h. In addition, light:dark grown thalli were transferred into continuous dim or strong light or darkness, in order to check whether or not the rhythms continued under these conditions. By taking photomicrographs of intact thalli and of isolated cortical cell layers, prepared by bisecting, it could be shown that the maxima and minima of circadian transmittance changes correspond well with the number of phaeoplasts at the periclinal cell walls. The ecological relevance of these phenomena is discussed.
    Type of Medium: Electronic Resource
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  • 12
    Electronic Resource
    Electronic Resource
    Springer
    Marine biology 51 (1979), S. 77-82 
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The occurrence of light-induced chromatophore displacements and concomitant transmittance changes in marine algae was investigated by microscope and photometrically with an automated recording microphotometer system; 16 brown, 6 green and 20 red algae were studied. In most of the brown algae, both phaeoplast displacements and transmittance changes were found. In some red algae which are frequently exposed to direct sun light during emergence at low tide, light-induced transmittance changes were measured, but they could not unequivocally be correlated with changes in the position of rhodoplasts. Among green algae, only Ulva lactuca shows chloroplast displacements which, however, follow circadian rhythms and are consequently not light-induced in the strict sense. The dose-response curves of light-induced chromatophore displacements were measured in the following Fucus and Laminaria species: F. spiralis, F. vesiculosus, F. serratus, L. digitata, L. saccharina and L. hyperborea. While in Fucus species correlations between light-induced transmittance changes and zonation of the intertidal area seem to exist, no significant differences have been found in the Laminaria species. The physiological role and ecological importance of light-induced chromatophore displacements for seaweeds living in the intertidal belt are discussed.
    Type of Medium: Electronic Resource
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  • 13
    ISSN: 1432-1211
    Keywords: Key words Major histocompatibility complex ; DQA ; Sigmodon hispidus ; Muridae ; Allelic diversity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  The cotton rat (Sigmodon hispidus) is a common murid rodent of the southern United States, Mexico, and Central America. Using single-stranded conformation polymorphism analysis and DNA sequencing techniques, 11 DQA exon 2 alleles were detected among 180 S. hispidus from Caddo County, Oklahoma, USA. The alleles represent a single locus exhibiting a high level of polymorphism. Nucleotide and amino acid distance values among DQA alleles of S. hispidus were higher than those within Mus musculus and species of Rattus. Although the distribution of polymorphic amino acid residues among alleles of S. hispidus was similiar to that of Mus and Rattus, some residues of the α-helix region were more variable in S. hispidus. Comparisons of nonsynonymous and synonymous substitutions indicated a trend toward higher numbers of nonsynonymous substitutions; however, this difference was not significant statistically among S. hispidus alleles. To examine evolution of DQA alleleswithin Muridae, we performed a phylogenetic analysis that included DQA alleles from S. hispidus, Peromyscus leucopus, M. musculus, R. norvegicus, and six Australian species of Rattus. Results depicted monophyly for each genus, and this concordance between species and gene trees represents a lack of evidence for trans-species persistence of alleles among these genera.
    Type of Medium: Electronic Resource
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  • 14
    Electronic Resource
    Electronic Resource
    Springer
    Archives of microbiology 144 (1986), S. 393-397 
    ISSN: 1432-072X
    Keywords: Chlamydomonas reinhardtii ; Phototaxis ; Motility ; Flagellates ; Flagellar movement ; Calcium ; Calcium channel blockers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effects of the four calcium channel blockers flunarizine, verapamil, diltiazem and nimodipine on motility and phototaxis of Chlamydomonas reinhardtio have been tested with a fully automated and computerized population system. Flunarizine inhibits motility transiently by causing the detachement of the flagella which, however, are regenerated during some hours. Phototaxis is inhibited to the same extent, but this is simply the result of the decreased motility and, hence, a non-specific effect. Verapamil causes also a detachement of the flagella with following regeneration, but in addition motility and phototaxis are inhibited by this drug to different extents, indicating the involvement of calcium channels in both processes. Diltiazem and nimodipine inhibit phototaxis without impairing motility, indicating that both processes are regulated in different ways. If diltiazem and nimodipine are applied simultaneously, no additive inhibitory effect can be observed. However, the combination of both blockers with verapamil causes and additive inhibitory effect as if verapamil is applied alone. By increasing the external calcium concentration from 10-4 M to 10-3 M the optimum of positive phototaxis is shifted to higher fluence rates. This shifting occurs also in the presence of channel blockers, but the strength of the positive reaction is influenced. These results point to the involvement of calcium channels in both phototaxis and motility, but simultaneously demonstrate the different sensitivity of the two processes to these drugs.
    Type of Medium: Electronic Resource
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  • 15
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 194 (1962), S. 894-895 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Earlier workers disrupted vaccinia by treatment with 1 per cent sodium carbonate3 or 5 per cent sodium hydroxide4. In our hands these classic methods, which were originally applied to virus cultivated on rabbit skin, released less than 1 per cent of the total DNA from the egg-adapted Levaditi ...
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  • 16
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Archives of Biochemistry and Biophysics 106 (1964), S. 343-347 
    ISSN: 0003-9861
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 17
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    BBA Specialized Section on Nucleic Acids and Related Subjects 55 (1962), S. 271-272 
    ISSN: 0926-6550
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 18
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Tetrahedron: Asymmetry 5 (1994), S. 1459-1462 
    ISSN: 0957-4166
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 19
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Physica B+C 81 (1976), S. 395-402 
    ISSN: 0378-4363
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 20
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Journal of Chromatography B: Biomedical Sciences and Applications 570 (1991), S. 65-76 
    ISSN: 0378-4347
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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